Specialized Functions & Structures: Differences Between Organisms

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

All organisms have many of the same basic needs and perform the same functions such as eating, drinking, and reproducing. In this lesson we'll look at how different organisms accomplish these tasks with different structures that in the end lead to the same result.

Different Yet the Same

Take a look at the living things around you. Even though you look different from a fish or a bird or a fern, deep down we are all the same. I don't mean in the sense that you are going to be able to fly to your friend's house or photosynthesize. No, we're all the same in the sense that we are all made of cells, the building blocks of life. The differences lie in the fact that cells are specialized. This means that they are designed differently so that they can perform different functions. For example, your muscle cells have a very different function than your nerve cells, just like your heart cells are different from your liver cells for the same reason. And because the structures that are made up of specialized cells are also designed for specific functions we can say with confidence that the structures themselves are specialized too.

The Same Yet Different

When we look at different organisms we often see that many of the same functions, such as breathing, eating, and movement, are performed by structures that are not the same. This is because different organisms have developed unique structures that perform these functions, and that do so in ways that fit their specific environments. So in this case, the structures are specialized to perform a specific function but also to fit the needs of a specific organism.

Let's look at some examples to see what's going on here. Take breathing for example. You breathe air through your mouth and that air travels down your throat and into your lungs. But a fish uses gills to accomplish this task. Amphibians breathe through lungs like us, but they can also exchange gases through their skin! Plants 'breathe' as well and they do this by exchanging gas through pores in their leaves called stomata.

Plants use stomata to exchange gas, much like we use our mouths to let air in and out.
plant stoma

Animals have to excrete waste products from food and metabolic processes. Some animals, like mammals, have a complex urinary system that produces liquid waste, and is separate from the intestines which produce solid waste. We have a specialized structure called a urethra that allows urine to pass from our bodies. A bird also produces waste, but it doesn't have a separate system for liquid and solid waste and both come out together through its cloaca. Fish also have a highly specialized waste system but theirs is designed to excrete ammonia as a waste product, instead of urea or uric acid. This is a highly toxic substance but because they are in aquatic systems they can produce this waste safely because it gets diluted very quickly in the surrounding water.

All organisms need to reproduce if they want to pass on their genes to the next generation. How this is done varies greatly from one organism to the next. And again, the end result is the same even though the structures that perform this task are quite different. While many organisms reproduce sexually, meaning that an egg is fertilized by a sperm, others reproduce asexually, which is when a genetically identical individual is created from only one parent. Some animals fertilize internally, while some fertilize externally. Some animals have elaborate reproductive structures while others are quite minimal. Plants reproduce as well, though because they can't move around they depend on other organisms to help them. These structures are designed to attract pollinators that help facilitate reproduction.

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